When we're talking about a piece of writing, music, or film, edited means corrected, amended, or changed (hopefully for the better). Edited is also sometimes used to mean shortened or censored.
A book that's been edited has gone through all sorts of corrections. First it gets rearranged, shortened, added to, made more clear, sometimes rewritten. Then it gets edited by a copy editor for factual truth, spelling, consistency, and clarity. A song might get edited for play on the radio, or raw film footage edited for the nightly news. And if you hear a "bleeeeep!" during your favorite talk show, it's likely that a bad word has been edited out.